Process for dressing ores



PROCESS FOR DRESSING onns Olav Moklebust, Hauge I Dalane, Norway, assignor, by mesne assignments, to R-N Corporation, New York, N.Y., a corporation of Deiaware No Drawing. Filed June 1, 19153, Ser. No. 358,981

Claims priority, application Norway July 8, 1952 4 Claims. (Cl. 241-14) This invention relates to ore dressing. More particularly it relates to a process for separating soft iron oxides from gangue material normally present in iron-containing ores.

Certain; sedimentary iron ores, such as for instance, hematite, consist of gangue material like quartz intimately dispersed, in the form of grains and bands, with iron oxides which may also be in the form of grains and bands The quartz component is'usually crystalline in nature and relatively hard compared to the iron oxides. In many ores, as for instancedeconiposed hematite ores and ochre, the iron oxides may even have a soft earthlike consistency. I

It is customary when dressing such'iron containing'ores by conventional methods to crush the ore until the grains or gangue and iron oxide are liberated and then to separate same. In so doing, both components, i.e. the gangue and the iron oxides must be crushed to extremely small particle size, and if the separation is carried .out in the wet state, a slimy suspension will be formed because of the particle size with the result that ultimate separation of gangue and iron oxides becomes very difficult. Assuming that separation is possible the fine, slimy iron oxides must subsequentlyibe dewatered by the employment of settling arid filtration steps, and such action normally results in relatively high iron oxide losses and enerally inefficient separation and recovery.

Accordingly an object of the instant invention is to provide an improved process for separating the gangue and soft iron oxide fractions of iron-containing ores. Another object is to provide a process for dressing ironcontaining ore material wherein one avoids formation of slimy suspensions which are only further processed with difficulty. These and other objects of the instant invention will become obvious from the following more com plete description.

Broadly the instant invention relates to a process for dressing iron oxide-containing materials which comprises crushing said materials to form small discrete particles, pugging said particles in the presence of water whereby a substantial portion of the soft iron oxide is liberated from the gangue constituents of said materials, and subsequently separating said iron oxide from said gangue constituents. I, a

The present invention is based on the utilization of the difference in hardness of the gangue and iron oxide components. The ore is crushed for instance to 1 mm. particle size and subjected to pugging in the presence of water. In this operation the particles are rubbed and pugged against each other. The soft iron oxides which are present on the surface of the quartz grains are torn loose from the harder quartz grains and suspended in the water. One would expect that by this treatment only part of the iron oxides which is present at the surface of the quartz grains would be torn loose. However it has been determined by the practice of the instant invention,- that the soft iron oxides which are present in-the quartz Fatented Apr. 18, 1 951 grains are also washed out and suspended in the water. The exact mechanism by which this is accomplished is not known; however the water penetrates through pores and channels to the soft iron oxides in the quartz grains, and it is postuated that in the course of the pugging operation a pulsation action occurs with the application of alternate pressure and suction forces on the quartz grains. The iron oxides are transferred to a pulpy consistency and are drawn out of the quartz grains by the pulsation effect.

It has been found that the material should be maintained in rather thick pulp form in order to obtain maximum benefit of the pulsation effect during the pugging action. In this respect it has been found preferable to add water as required in 'order to maintain an amount corresponding to about 5 0% by weight of the pulp.

As the amount of iron oxide which is transferred to the pulp is increased, more water must be added to obtain the desired pulsating effect. Eventually a thick suspension is obtained, consisting of coarse grains of gangue and a pulp of finely divided iron oxide which can be separated by a settling operation, centrifuging, or similar methods. The grains of gangue which may still contain some small amount of iron oxide in the form of hard grains, separate out as a precipitate, and this precipitated material may be treated further to remove the iron oxide content according to lmown processes.

it is desirable to maintain a thick pulp of the iron oxide after removing the gangue in order to subject it directly to filtering. Thus .it willbe possible to-avoid losses which may occur by settling fine iron oxidesgrains from a thin pulp in order toconcentratethe fluid portion suificiently to make the filtration a practical operation. After recovering theiron oxides, they may be dried and processed as known in theart. material is then suit-able for employment, as for example in smelting operations.

The following examples are given to illustrate the instant invention more clearly:

Example I A hematite ore of the taconite type consisting substantially of quartz and iron oxide (Fe O was used as a raw material. The iron oxides were present partly as finer and coarser bands and partly as very finely impregnated grains in the quartz. very soft, While the :rest, especially the larger grains and bands, were hard inside. The iron content of the ore was approximately 38% Fe and consequently too low for direct smelting in a blast furnace. The ore was crushed to approximately 1 mm. particle size :and transferred to the rubbing or pugging apparatus, which in this case was a horizontal trough with a rotating screw similar to a transport screw. The ore was fed continuously to the apparatus at one end and was transported through the apparatus by the screwing action, while at the same time it was pu-gged and rubbed. During this treatment water was gradually added so that the mass in the apparatus attained a thick consistency. The total amount of water added was approximately 50% of the weight of the ore. After the mass had passed through the apparatus, it was subjected to settling without further dilution, whereby the coarser grains, i.e. grains over approximately mesh, were removed.

The amount of ironoxide recovered from the ore by the pugging operation was 36.8% by Weight containing The iron recovery was 48.5% of the total amount of iron in'the original ore.

The coarse grains consisted partly of free grains of gang'ue and free grains of iron oxides and partly of grains of gangue containing larger or smaller amounts of iron ox de. The iron content of thiscoarser fraction was Some of the iron oxides were.

approximately 31% Feand was present mainly in the form of hard grains. Thisiradtion was subjected to the usual crushing'and dressing:

Theiron oxide pulp was filtered, dried and agglomerated. The agglomerate contained approximately 50% Fe and would therefore correspond to a low grade blast furnace ore. g

' I Example [I 7 The raw material in this case was a titaniferous ore concentrate of approximately 20mesh containing 44% TiO combined iron .ofthe ilmenite (FeOTiO to free iron 7 oxide by reduction and subsequentreoxidation and were now present ina very' finely diyidedfstate intpores and channels in the. grains of ore., It was desired to remove by the embodiments and ex ing said ore to form small discreet particles, pugging said 'The soft iron oxides'had been formed by transferring the the iron'oxides in order to obtain a titanium concentrate methods did not give asatisfactory result.

The material'was pugged while water was gradually added. .The total amount of water was 'of the weight of the pulp. The product was then classified and separated and gave a titanium concentrate containing TiO and an iron oxide concentrate containing 66% Fe. The test shows that practically all the soft iron oxides had beensuspenfded and separated from the 'ti- 7 with a higher content of TiO but the usual washing tanium concentrate. The actual pugging operation in this caseonly took approximately 10 minutes. 7

In contrast atest carried out with the same sort o I 7 raw material in a rotating washing. drum with equal parts 'by weight of ore and water after 1 hours treatment gave -a titanium concentrate containing only. 60% TiO In,

this case only 26% of the soft iron roxidesr was extracted.

'It been demonstrated that by employing the process. of the instant invention it is' possible to recover thesoft iron oxide portion of iron-containing ores in good yield.- .While this invention has been described and illustrated particles in the presence of water thereby withdrawing iron oxides fronithe interior of the gangue component, and forming a pulp of soft iron particles so liberated without decreasing the size of the ground gangue particles, subsequently separating the iron oxide slurry from the gangue component and recovering the iron oxide from the water, the total amount'of' watenemployed' in the pugging operation being approximatelyfifty percent by weight'of the iron oxide pulp. p 7

2. Process according to claim 1 wherein the gangue constituents are separated from the'liberated iron oxides by a settling operation.

3. Process according as claiml wherein thegangue constituents are separated from the liberatediron oxides by a centrifuging action. V

4. Process according to claim l whereinsaid iron containing materials are crushed to approximately 1 millimeter particle size;

.References'inthefile ofthis patent 5 V STATES PATENTS. 7

860,811] Little etal. May 31, 1932 l,92l-,306 7 Aldrich i. Aug. 8, 1933 2,3085917 v Hardinge Jan. 19, 1943 j 1 OTHER REFERENCES 7 Engineering and Mining Journal; January 1950, pagm 

1. A PROCESS FOR DRESSING ORE AND SEPARATING SOFT IRON OXIDES CONTAINED IN THE INTERIOR CHANNELS OF A RELATIVELY HARD GANGUE COMPONENT OF THE ORE WHICH COMPRISES CRUSHING SAID ORE TO FORM SMALL DISCREET PARTICLES, PUGGING SAID PARTICLES IN THE PRESENCE OF WATER THEREBY WITHDRAWING IRON OXIDES FROM THE INTERIOR OF THE GANGUE COMPONENT, AND FORMING A PULP OF SOFT IRON PARTICLES SO LIBERATED WITHOUT DECREASING THE SIZE OF THE GROUND GANGUE PARTICLES, SUBSEQUENTLY SEPARATING THE IRON OXIDE SLURRY FROM THE GANGUE COMPONENT AND RECOVERING THE IRON OXIDE FROM THE WATER, THE TOTAL AMOUNT OF WATER EMPLOYED IN THE PUGGING OPERATION BEING APPROXIMATELY FIFTY PERCENT BY WEIGHT OF THE IRON OXIDE PULP. 